|Title||Campanian-Maastrichtian clay-rich sequences along the North Pacific margin: key sequences for early cooling history of Cretaceous greenhouse Earth|
|Author||Hasegawa, T; Moriya, K; Haggart, J W|
|Source||Geological Society of America, Abstracts With Programs vol. 45, no. 7, 2013 p. 245|
|Links||Online - En ligne|
|Alt Series||Earth Sciences Sector, Contribution Series 20130166|
|Publisher||Geological Society of America|
|Meeting||Geological Society of America, Annual Meeting; Denver; US; November 4-7, 2013|
|Media||paper; on-line; digital; diskette|
|Province||Western offshore region|
|Area||North Pacific; Japan; Russian Federation; Canada; United States|
|Lat/Long WENS||-163.0000 167.0000 59.0000 32.0000|
|Subjects||paleontology; geochronology; stratigraphy; Upper Cretaceous; Campanian; Cenomanian; Coniacian; Maastrichtian; biostratigraphy; carbon isotopes; fossil assemblages; fossil distribution; Yezo Group;
Nanaimo Group; Mesozoic; Cretaceous|
|Program||Frontier basin analysis, Geoscience for New Energy Supply (GNES)|
|Abstract||Cretaceous shelf and fore-arc basin sandstone and mudstone are preserved in the coastal regions of Japan, Far East Russia, and the Pacific coast of Canada and USA. Several of these sequences have been
variously assessed in terms of their biostratigraphy and chemostratigraphy, and correlated to the Aptian through Maastrichtian. In addition to macro- and microfossil biostratigraphy, carbon isotope (del13C) stratigraphy has also identified some
important event horizons within these successions, such as OAE2. Owing to the clay-rich nature of the strata, parts of the sequences yield excellently preserved calcareous fossils available for oxygen isotope thermometry (Moriya et al.,
This study examines the Campanian-Maastrichtian interval. Its chronostratigraphy, including detailed ?13C stratigraphy, has been summarized recently (Voigt et al., 2012) and it records the initial phase of global cooling of the
Cretaceous greenhouse Earth (Moriya, 2011; Friedrich et al., 2012). As the northern paleo-Pacific Ocean had a large heat capacity, its paleoceanography should provide insights for understanding the subsequent environmental transition from greenhouse
to ice house Earth.
The Yezo Group and its equivalent in Hokkaido (Japan) and Sakhalin (Russian Far East), as well as the Nanaimo Group of the Canadian Pacific coast (British Columbia), are examined in this study. From the Yezo Group, a clear
negative ?13C excursion as large as 1.4¿2 per mil has been identified.
On Sakhalin, its Campanian-Maastrichtian boundary age is constrained by local bio- and magnetostratigraphy, and the excursion is thus identified as the Campanian
Maastrichtian Boundary Event (CMBE), associated with some subevents.
Del13C stratigraphy of the Nanaimo Group is under analysis. On the basis of magneto- and biostratigraphy (Haggart et al., 2011; Ward et al., 2012), the CMBE interval is
expected to be located in the mudstone-dominated intervals of the overlying Northumberland or Spray formations.
|Summary||(Plain Language Summary, not published)|
This is an abstract of a talk to be presented at a scientific meeting. The Nanaimo basin of British Columbia includes potential hydrocarbon-bearing
sedimentary rocks that accumulated between 85-65 million years ago. These rocks contain organic matter, from which oil and natural gas may ultimately develop, as well as the fossil shells of microscopic organisms that lived in the world¿s oceans at
the time. The authors have analyzed the isotopic composition of these shells and the sediment they are found in and have identified shifts in the isotopic compositions through time. They interpret these shifts in terms of changing ocean water
temperatures and levels of carbon dioxide in the atmosphere. The new data show that the Cretaceous Nanaimo basin rocks are rich in organic matter and also exhibit warming and cooling trends which are similar to patterns recognized in other areas.
These patterns help to more precisely correlate the rocks of the Nanaimo basin both locally and globally, and provide a better understanding of the potential for hydrocarbon formation in western Canada.